function changeBg(){
	var obj = document.getElementById("chbg"); //定位id

	var index = obj.selectedIndex; // 选中索引

	var text = obj.options[index].text; // 选中文本

	var value = obj.options[index].value; // 选中值
	if(value==0||value==1){
		document.getElementsByTagName("html")[0].className="bgImg x-strict"; 
	}
	if(value==2){
		document.getElementsByTagName("html")[0].className="bgImg2 x-strict"; 
	}
	if(value==3){
		document.getElementsByTagName("html")[0].className="bgImg3 x-strict"; 
	}
	if(value==4){
		document.getElementsByTagName("html")[0].className="bgImg4 x-strict"; 
	}
	if(value==5){
		document.getElementsByTagName("html")[0].className="bgImg5 x-strict"; 
	}
	if(value==6){
		document.getElementsByTagName("html")[0].className="bgImg6 x-strict"; 
	}
	if(value==7){
		document.getElementsByTagName("html")[0].className="bgImg7 x-strict"; 
	}
	if(value==8){
		document.getElementsByTagName("html")[0].className="bgImg8 x-strict"; 
	}
	if(value==9){
		document.getElementsByTagName("html")[0].className="bgImg9 x-strict"; 
	}
	if(value==10){
		document.getElementsByTagName("html")[0].className="bgImg10 x-strict"; 
	}
	if(value==11){
		document.getElementsByTagName("html")[0].className="bgImg11 x-strict"; 
	}
	if(value==12){
		document.getElementsByTagName("html")[0].className="bgImg12 x-strict"; 
	}
	if(value==13){
		document.getElementsByTagName("html")[0].className="bgImg13 x-strict"; 
	}
	if(value==14){
		document.getElementsByTagName("html")[0].className="bgImg14 x-strict"; 
	}
	if(value==15){
		document.getElementsByTagName("html")[0].className="bgImg15 x-strict"; 
	}
	if(value==16){
		document.getElementsByTagName("html")[0].className="bgImg16 x-strict"; 
	}
	if(value==17){
		document.getElementsByTagName("html")[0].className="bgImg17 x-strict"; 
	}
	if(value==18){
		document.getElementsByTagName("html")[0].className="bgImg18 x-strict"; 
	}
	if(value==19){
		document.getElementsByTagName("html")[0].className="bgImg19 x-strict"; 
	}
	if(value==20){
		document.getElementsByTagName("html")[0].className="bgImg20 x-strict"; 
	}
	if(value==21){
		document.getElementsByTagName("html")[0].className="bgImg21 x-strict"; 
	}
	if(value==22){
		document.getElementsByTagName("html")[0].className="bgImg22 x-strict"; 
	}
	if(value==23){
		document.getElementsByTagName("html")[0].className="bgImg23 x-strict"; 
	}
	if(value==24){
		document.getElementsByTagName("html")[0].className="bgImg24 x-strict"; 
	}
	if(value==25){
		document.getElementsByTagName("html")[0].className="bgImg25 x-strict"; 
	}
	if(value==26){
		document.getElementsByTagName("html")[0].className="bgImg26 x-strict"; 
	}
	if(value==27){
		document.getElementsByTagName("html")[0].className="bgImg27 x-strict"; 
	}
	if(value==28){
		document.getElementsByTagName("html")[0].className="bgImg28 x-strict"; 
	}
	if(value==29){
		document.getElementsByTagName("html")[0].className="bgImg29 x-strict"; 
	}
	
	if (window.localStorage) {
	    localStorage.setItem("login_bg_image", value);	
	} else {
	    Cookie.write("login_bg_image", value);	
	}
}
window.onload=function(){
	var strStoreDate = window.localStorage? localStorage.getItem("login_bg_image"): Cookie.read("login_bg_image");
	if(strStoreDate==0||strStoreDate==1){
		document.getElementsByTagName("html")[0].className="bgImg x-strict";
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==2){
		document.getElementsByTagName("html")[0].className="bgImg2 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==3){
		document.getElementsByTagName("html")[0].className="bgImg3 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==4){
		document.getElementsByTagName("html")[0].className="bgImg4 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==5){
		document.getElementsByTagName("html")[0].className="bgImg5 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==6){
		document.getElementsByTagName("html")[0].className="bgImg6 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==7){
		document.getElementsByTagName("html")[0].className="bgImg7 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==8){
		document.getElementsByTagName("html")[0].className="bgImg8 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==9){
		document.getElementsByTagName("html")[0].className="bgImg9 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==10){
		document.getElementsByTagName("html")[0].className="bgImg10 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==11){
		document.getElementsByTagName("html")[0].className="bgImg11 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==12){
		document.getElementsByTagName("html")[0].className="bgImg12 x-strict";
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==13){
		document.getElementsByTagName("html")[0].className="bgImg13 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==14){
		document.getElementsByTagName("html")[0].className="bgImg14 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==15){
		document.getElementsByTagName("html")[0].className="bgImg15 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==16){
		document.getElementsByTagName("html")[0].className="bgImg16 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==17){
		document.getElementsByTagName("html")[0].className="bgImg17 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==18){
		document.getElementsByTagName("html")[0].className="bgImg18 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==19){
		document.getElementsByTagName("html")[0].className="bgImg19 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==20){
		document.getElementsByTagName("html")[0].className="bgImg20 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==21){
		document.getElementsByTagName("html")[0].className="bgImg21 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==22){
		document.getElementsByTagName("html")[0].className="bgImg22 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==23){
		document.getElementsByTagName("html")[0].className="bgImg23 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==24){
		document.getElementsByTagName("html")[0].className="bgImg24 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==25){
		document.getElementsByTagName("html")[0].className="bgImg25 x-strict"; 
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==26){
		document.getElementsByTagName("html")[0].className="bgImg26 x-strict";
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==27){
		document.getElementsByTagName("html")[0].className="bgImg27 x-strict";
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==28){
		document.getElementsByTagName("html")[0].className="bgImg28 x-strict";
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else if(strStoreDate==29){
		document.getElementsByTagName("html")[0].className="bgImg29 x-strict";
		document.getElementById("chbg").options[strStoreDate].selected=true;
	}else{
		//默认皮肤
		document.getElementsByTagName("html")[0].className="bgImg19 x-strict"; 
		document.getElementById("chbg").options[0].selected=true;
	}
}